Catalyzed propellant compositions of high burning rate



United States Patent 3,240,640 CATALYZED PROPELLANT COMPOSITIONS OF HIGH BURNING RATE Edwin K. Ives, Columbus, Ind., assignor to Standard Oil Company, Chicago, 11]., a corporation of Indiana N0 Drawing. Filed Nov. 18, 1963, Ser. No. 324,217 4 Claims. (Cl. 149-19) This invention relates to ammonium nitrate compositions suitable for use as gas generating materials, and particularly an ammonium nitrate composition which exhibits a high burning rate when utilized as a gas generator.

Ammonium nitrate base propellant materials are used for gas generation purposes where the exhaust gas from the combustion of the propellant is used to drive a turbine prime mover. In many instances, it is very important that the propellant generate the exhaust gas at a high rate in order to more rapidly bring the rotation of the turbine up to the desired speed or to drive the turbine at a high speed. Previous propellants have not been entirely satisfactory in their burning rates for the generation of the exhaust gas.

Briefly, the invention is directed to an ammonium nitrate propellant composition which exhibits a high and improved burning rate. The composition consists essentially of about 3-7 weight percent of polyvinyl acetate, about 2-5 weight percent of dinitrophenyl propyl ether, or similar ether, about 1-4 weight percent of carbon, about 4-5 weight percent of a burning rate catalyst made up of about 1-3 weight percent of ammonium dichromate, about 2-4 weight percent of copper chromite, and about 0.2 weight percent of copper powder, about 4-7 weight percent of aluminum, about 3-6 Weight percent of boron, about 5-15 weight percent of sodium dinitrosalicylate, and the remainder being essentially ammonium nitrate.

The term ammonium nitrate as used in this specification and in the claims is intended to mean either c.p. grade or ordinary commercial grade ammonium nitrate or military grade. The particles may be coated with a small amount of moisture-resisting material such as petrolatum or parafiin. A minor amount of other inorganic nitrates such as sodium nitrate and/or potassium nitrate may be present. Finely ground ammonium nitrate is preferred.

The binder material utilized in the instant composition consists of polyvinyl acetate and, as a modifier and plasticizer, dinitrophenyl propyl ether. Other suitable ethers include dinitrophenoxy ethanol, dinitro diphenyl oxide, and dinitro propenyl ether.

The carbon component of the composition is described on pages 3-4 of copending application S.N. 219,735, filed August 27, 1962, now Patent No. 3,126,304, which are incorporated into and made a part of this specification by reference. The preferred carbons are the highly adsorptive activated carbons and the carbon blacks described in the above reference.

A burning rate catalyst is also present in the composition and is made up of ammonium dichromate and copper chromite. Copper powder may also be present to replace part of the previous two catalysts. Based on a total of 5 weight percent of the total composition as catalyst, at least about 1 weight percent is ammonium dichromate, at least about 2 weight percent is copper chromite, and the remainder is essentially ammonium dichromate, copper chromite, copper powder or mixtures thereof.

The burning rate catalyst should be in a finely divided form. Commonly, a pulverized ammonium dichromate from a hammermill and copper chromite and copper powder in the order of about 200 mesh (Tyler) are very suitable.

Additional components include aluminum and boron particles, usually from about 35-115 mesh (Tyler) for the aluminum and about -200 mesh (Tyler) for the boron. Normally, boron is in an amorphous form.

The composition also includes sodium dinitrosalicylate as a catalyst. This catalyst is described on pages 1-2 of copending application S.N. 219,741, now Patent No. 3,152,936, filed August 27, 1962, which are incorporated into this application by reference.

Example I An ammonium nitrate composition was prepared from approximately 4 weight percent of polyvinyl acetate, 3 weight percent of dinitrophenyl propyl ether, 2 Weight percent of carbon black, 2 weight percent of ammonium dichromate (from hammermill), 2 weight percent of copper chromite (about 200 mesh), 6 weight percent of aluminum (about 35-100 mesh), 4 weight percent of amorphous boron (about 100-200 mesh), and 10 weight percent of sodium dinitrosalicylate.

The composition was prepared by mixing together for one hour in a laboratory mixer a l-quart batch having ingredients in the proportions set forth above. The mixing temperature was held below C. Approximately 1 pound of composition was prepared.

After mixing, the resulting mass was compression molded and subsequently sawed into strips for the burning rate test. The burning rate tests were conducted in a Crawford bomb pressured with nitrogen at various levels and at 25 C.

A burning rate of 0.43 inch per second at 1000 p.s.i.a. was obtained in the test. This was remarkable since a previous propellant, considered to have a high burning rate, had a rate of only 0.28 inch per second at 1000 p.s.i.a.

The test composition also exhibited a pressure exponent of 0.56 and a specific impulse of 225 seconds. The pressure exponent is the slope of the curve obtained by plotting pressure versus burning rate on log-10g paper. Pressure exponents below the common values of 0.58-0.60 and specific impulses above the common values of -210 seconds are highly desirable. These characteristics further demonstrate the advantages of the test composition. The composition exhibits a high enough rate and specific impulse so that it could be used for direct propulsion as well as a gas generator.

Thus, having described the invention, what is claimed 1. A solid composition consisting essentially of polyvinyl acetate, about 3-7 weight percent; an ether selected from at least one member of the class consisting of dinitrophenyl propyl ether, dinitrophenyl propenyl ether, dinitrophenoxy ethanol, and dinitro diphenyl oxide, about 2-5 weight percent; carbon, about 1-4 weight percent; a burning rate catalyst, about 4-5 weight percent, said catalyst having about 1-5 weight percent of ammonium dichromate, about 2-5 weight percent of copper chromite, and 0.2 weight percent of copper powder; aluminum,

about 4-7 weight percent; boron, about 3-6 weight percent; sodium dinitrosalicylate, about 5-15 weight percent; and the remainder of said composition being essentially ammonium nitrate.

2. The composition of claim 1 wherein said ether is dinitrophenyl propyl ether.

3. The composition of claim 1 wherein said burning rate catalyst contains only ammonium dichromate and copper chromite.

4. A solid composition consisting essentially of polyvinyl acetate, about 4 Weight percent; dinitrophenyl propyl ether, about 3 weight percent; carbon black, about 2 weight percent; ammonium dichromate, about 2 weight percent; copper chromite, about 2 weight percent; aluminum, about 6 weight percent; boron, about 4 weight percent; sodium dinitrosalicylate, about 10 weight percent; and the remainder of said composition being essentially ammonium nitrate.

No references cited.

CARL D. QUARFORTH, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,240,640 March 15, 1966 Edwin K. Ives It is hereby certified that error appears in the above numbered pai ent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 33 and column 2, line 65, for "0.2" each occurrence, read 02 Signed and sealed this 11th day of April 1967.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A SOLID COMPOSITION CONSISTING ESSENTIALLY OF POLYVINYL ACETATE, ABOUT 3-7 WEIGHT PERCENT; AN ETHER SELECTED FROM AT LEAST ONE MEMBER OF THE CLASS CONSISTING OF DINITROPHENYL PROPYL ETHER, DINITROPHENYL PROPENYL ETHER, DINITROPHENOXY ETHANOL, AND DINITRO DIPEHNYL OXIDE, ABOUT 2-5 WEIGHT PERCENT; CARBON, ABOUT 1-4 WEIGHT PERCENT; CATALYST HAVING ABOUT 1-5 WEIGHT PERCENT OF AMMONIUM DICHROMATE, ABOUT 2-5 WEIGHT PERCENT OF COPPER CHROMITE, AND 0.2 WEIGHT PERCENT OF COPPER POWDER; ALUMINUM, ABOUT 4-7 WEIGHT PERCENT; BORON, ABOUT 3-6 WEIGHT PERCENT; SODIUM DINITROSALICYLATE, ABOUT 5-15 WEIGHT PERCENT; AND THE REMAINDER OF SAID COMPOSITION BEING ESSENTIALLY AMMONIUM NITRATE. 